My U.S. Pat. No. 3,870,625 relates to a process for the regeneration of used lubricating oil, consisting of spraying said oil in pulsed form at the top of a first column in which propane is introduced in a counterflow to said oil, then passing the mixture of oil, propane and oil dissolved in propane, successively into a plurality of columns disposed in series, at the top of one of which, at least, propane is introduced in pulsations counterflowing to said mixture, removing from the base of said columns the impurities which are there deposited by gravity, recovering from the last column the solution of oil in the liquid propane, and separating the oil, thus purified, from said liquid propane by vaporization of the latter.
In order to ensure a better contact between the liquid propane and the oil to be regenerated, mechanical vibrations are preferably imparted to said columns.
The vaporized propane, at the end of the treatment of the oil, is then liquified by compression, so as to be recycled into the high pressure circuit in liquid state.
My U.S. Pat. No. 3,870,625 also describes a device for the implementation of this process.